Pesticides are useful in protecting plants from attack by various pests including insects. A disadvantage of many pesticides currently marketed are the (perceived or otherwise) issues associated with chemicals and environmental concerns. Another problem is that the chemicals require special handling and may be poisonous or harmful to the person applying the chemical. Ideally, pesticides would be common-place, have no or minimal environmental effects and utilise protection mechanisms already present in nature referred to herein as ‘naturally’ produced.
Alkaloids, including pyrrolizidine alkaloids, are produced by endophytes as a fungal metabolite when in symbiotic relationships with plant species including grasses. Such endophytes are valued in grasses due to the pest protection the alkaloids produced from the endophytes provide. In effect, the endophyte provides the plant with a natural built in pest protection.
Typically, transferring resistance to another plant e.g. an alternative grass cultivar, has been carried out by infecting the plant with the endophyte. Examples of this process are described in other patents including those pursued by the applicant. A further example is U.S. Pat. No. 7,037,879 which teaches of a method of conferring pest resistance to plants of Poaceae by adding an isolated endophytic bacterium to the Poaceae plant. No teaching is made other than to transfer an endophyte similar to existing methods of transferring endophytic properties amongst grass cultivars. Inoculation may not always be easy or even possible between different plants. In addition, the pesticidal properties desired may not also transfer to other plants where inoculation is successful. It should also be appreciated that an inoculation step requires careful, slow and comparatively expensive techniques.
U.S. Pat. No. 6,372,239 teaches of a composition containing a ‘cocktail’ of plant alkaloids used as an insecticide. Alkaloids described include anabasine along with a wide variety of other alkaloids from a variety of plants. There is no teaching regarding the alkaloids being endophyte metabolites or the alkaloids being loline type compounds. The formulations described also utilise strong polar solvents with a preferred solvent being mineral turpentine. Such solvents are undesirable due to their cost and environmental impacts.
U.S. Pat. No. 5,185,028 teaches of synthetically produced N-substituted loline derivative compounds and their use as a pesticide in spraying applications. The specification teaches away from use of naturally derived alkaloid compounds claiming synthetic compounds with a differing C4 to C20 R1 group to naturally occurring pyrrolizidine alkaloid compounds. The specification also teaches that the synthetic loline derivative be mixed with strong solvents to form a liquid which, as noted above is not desirable. Further, the specification teaches that the solution should be applied at the locus for pesticidal effects such as by spraying on a leaf. Indirect methods of applications are not taught or contemplated in the specification.
Yates et al (1990)1 describes an experiment undertaken to determine the toxicity of tall fescue extracts where the tall fescue was infected with Acremonium coenophialum endophyte. Yates does not teach or suggest applying the extract to another plant in order to transfer pesticidal properties. Yates also does not attribute pesticidal properties to pyrrolizidine alkaloids. 1 Yates et al., ‘Assay of Tall Fescue Seed Extracts, Fractions and Alkaloids Using the Large Milkweed Bug’, J. Agric. Food Chem. 37:354-357 (1989).
US 2004/0141955 teaches of a novel endophytic fungi termed ‘Muscodor’ which is used to confer pest resistance to plants by inoculation of Muscodor species into the plant. A further option is described being use of a stabilised Muscodor placed adjacent or near the plant to be protected and the volatile compounds produced by the Muscodor provide the pesticidal effect. No disclosure is made regarding pyrrolizidine compounds, extracts of these compounds, or introducing these compounds into a plant. Pesticidal properties are only attributed to the Muscodor endophyte.
Casabuono et al 1997 teaches that loline alkaloids of Festuca argentine were asymptomatic and non-toxic at dose ranges from 31.25 to 125.0 mg/kg based on studies where such alkaloids were isolated and administered to mice as a concentrated aqueous suspension. No teaching is made within the paper regarding use of the isolated loline alkaloids as a pesticide. Of interest though is that loline alkaloids, whilst having a pesticidal affect, do not appear to be particularly toxic which may be useful in horticultural applications of the present invention.
From the above discussion, it should be appreciated that it would be desirable to have a pesticidal composition that utilised pesticidal protection mechanisms present in nature but without the need for example, to inoculate the plant with an endophyte.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.